Two factor authentication: something you know + something you have.
Apple is now offering this for your Apple ID here!
This is a must IMO for everyone who wants to protect their devices and data.
Google & Facebook also offer these services:
Google Facebook
Also check your banks & credit unions. They have been doing this for a whiles on the back end for employees with RSA tokens. Most now have some form of two factor authentication with an app or email of a one time code.
